1. Field of the Invention
This invention relates to a process for converting polymers terminating in a silyl ketene acetyl group to polymers that are terminally substituted by phosphonate groups via the reaction of the SKA. terminated polymers with vinyl phosphonates in the presence of a catalyst. The resulting polymers are useful as dispersants for pigments in acrylic finishes.
2. Discussion of the Prior Art
The vinyl phosphonates and SKA terminated polymers that are employed in the process of the present invention are known or obvious compounds.
The polymers terminating in silyl ketene acetals that are reactants for this process may be "living" polymers prepared by Group Transfer Polymerization (GTP), (Webster et al., "Group Transfer Polymerization--A New and Versatile Kind of Addition Polymerization", J. Am. Chem. Soc., 105, 5706 (1983)), including "living" polyunsaturated polymers (Hertler et al., "Group Transfer Polymerization with Polyunsaturated Esters and Silylpolyenolates", J. Am. Chem. Soc., 110, 5841 (1988)). GTP methods are fully described in U.S. Pat. Nos. 4,414,372; 4,417,034; 4,508,880; 4,524,196; 4,581,428; 4,588,795; 4,598,161; 4,605,716; 4,621,125; 4,622,372; 4,656,233; 4,656,226; 4,659,782; 4,659,783; 4,681,918; 4,695,607; 4,711,942; 4,728,706; 4,732,955; 4,736,003; 4,771,116; 4,771,117; 4,783,500; and in commonly assigned U.S. patent application Ser. No. 4,831 filed Jan. 13, 1987 and allowed Oct. 31, 1988, and in U.S. patent application Ser. No. 7,758 filed Jan. 26, 1987 and allowed Aug. 25, 1988. These patents and applications disclose processes for polymerizing an acrylic or maleimide monomer to a "living" polymer in the presence of:
(i) an initiator having at least one initiating site and which is a tetracoordinate organo(Si, Sn or Ge) compound, including such compound having at least one oxygen, nitrogen or sulfur atom attached to Si; and
(ii) a co-catalyst which is a source of fluoride, bifluoride, cyanide or azide ions or a suitable Lewis acid, Lewis basis or selected oxyanion.
The aforesaid patents and applications also disclose "capping" of "living" silyl ketene acetal groups with agents containing capping functions such as --CHO, --C(O)--, --NCO, --Br, --Cl and --TiCl.sub.3.
U.S. Pat. No. 4,508,880 (listed above) also discloses the preparation of poly(methyl methacrylate) polymers that are terminally substituted by phosphonate groups at the initiator end of the polymer chain by using phosphonate substituted silyl ketene acetals to initiate methyl methacrylate polymerization. Sogah et al., "Group Transfer Polymerization. Polymerization of Acrylic Monomers". Macromolecules, 20, 1473 (1987) discuss this same reaction in detail.
T. Ishihara et al., Tetrahedron Lett., 26, 79 (1985) disclose the reaction of silyl vinyl ethers with 2-perfluoroalkyl-2-fluoro vinyl phosphonates in essentially equimolar amounts to yield either perfluoroalkylpropargyl alcohols or substituted divinyl ethers, depending on the order of addition of reagents. Also disclosed is the reaction of 2-perfluoroalkyl-2-fluoro vinyl phosphonates with 2.5 molar equivalents of silyl vinyl ether in acetonitrile to yield 4-alkylidene-1,3-dioxolane derivatives.
None of the prior art disclosures teach the reaction of O-silyl ketene acetals--nonpolymeric in nature, or at the end of a polymer chain--with vinyl phosphonates.
The .alpha.,.omega.-diphosphonate (alpha,omega-diphosphonate) substituted compounds made via the present invention are unknown in the prior art.